An upflow water clarifier, such as those disclosed in Wyness U.S. Pat. Nos. 4,146,471 and 4,765,891, is a specific type of clarifier that has a prominent conical portion with the larger diameter at the upper end. Typically, the walls of the clarifier are angled at between about 40 degrees and 60 degrees with respect to the horizontal, although angles outside of this range can also be used. Contaminated water enters the clarifier near the lower end, while clarified effluent is removed from near the upper end. Inside, the water is given a rotational movement, often in part by feeding it into the clarifier in a tangential direction, resulting in a generally upward helical flow of the water within the clarifier.
The increasing diameter of the clarifier toward its upper end causes a decrease in velocity of the flow of liquid as it moves upwardly. As the velocity decreases, suspended solids having a higher density than water agglomerate and separate from the water, forming a revolving sludge blanket that remains behind as clarified water continues upward until being withdrawn as clarified effluent.
Conventionally, the effluent has been removed from the clarifier over weirs, and collected at one or more drop boxes at the periphery of the upper end of the clarifier, while sludge is periodically removed through a sludge concentrator located on the central axis of the clarifier. Traditionally, the sludge concentrator has taken the form of a cone suspended from an overhead observation deck that traverses the top of the clarifier, and has been used to concentrate and reduce the volume of the sludge before it is removed.